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Biomedical subjects

M Henze

Publications and source records attributed to M Henze.

49 records · Page 3Linked to original sources
PubMed2001

River Water Quality Model no. 1 (RWQM1): III. Biochemical submodel selection.

The new River Water Quality Model no. 1 introduced in the two accompanying papers by Shanahan et al. and Reichert et al. is comprehensive. Shanahan et al. introduced a six-step decision procedure to select the necessary model features for a certain application. This paper specifically addresses one of these steps, i.e. the selection of submodels of the comprehensive biochemical conversion model introduced in Reichert et al. Specific conditions for inclusion of one or the other conversion process or model component are introduced, as are some general rules that can support the selection. Examples of simplified models are presented.

Biochemical Phenomena↗
PubMed2001

PET imaging of somatostatin receptors using [68GA]DOTA-D-Phe1-Tyr3-octreotide: first results in patients with meningiomas.

UNLABELLED: Imaging of somatostatin receptors (SSTRs) using [111In]diethylenetriaminepentaacetic-acid-octreotide (DTPAOC) has proven to be helpful in the differentiation of meningiomas, neurinomas or neurofibromas, and metastases as well as in the follow-up of meningiomas. A drawback of the SPECT method is its limited sensitivity in detecting small meningiomas. Because of PET's increased spatial resolution and its ability to absolutely quantify biodistribution, a PET tracer for SSTR imaging would be desirable. METHODS: 1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetraacetic-acid-D-Phe1-Tyr3-octreotide (DOTATOC) was labeled using the positron-emitting generator nuclide 68Ga. We acquired dynamic PET images over 120 min after intravenous injection of 175 MBq [68Ga]DOTATOC in 3 patients suffering from 8 meningiomas (WHO I degrees; 7- to 25-mm diameter). Patients' heads had been fixed using individually shaped fiber masks equipped with an external stereotactic localizer system to match PET, CT, and MRI datasets. RESULTS: [68Ga]DOTATOC was rapidly cleared from the blood (half-life alpha, 3.5 min; half-life beta, 63 min). Standardized uptake values (SUVs) of meningiomas increased immediately after injection and reached a plateau 60-120 min after injection (mean SUV, 10.6). No tracer could be found in the surrounding healthy brain tissue. All meningiomas (even the 3 smallest [7- to 8-mm diameter]) showed high tracer uptake and could be visualized clearly. Tracer boundaries showed a good correspondence with the matched CT and MRI images. PET provided valuable additional information regarding the extent of meningiomas located beneath osseous structures, especially at the base of the skull. CONCLUSION: According to our initial experiences, [68Ga]DOTATOC seems to be a very promising new PET tracer for imaging SSTRs even in small meningiomas, offering excellent imaging properties and a very high tumor-to-background ratio.

Gallium Radioisotopes↗
PubMed2000

[Diagnostic evaluation of the breast using PET: optimization of data acquisition and postprocessing].

PURPOSE: Development and evaluation of an optimized protocol for PET examinations of the female breast with 2-F-18-fluoro-2-deoxyglucose (F-18-FDG). METHODS: All PET measurements were performed with a whole-body PET system (ECAT EXACT HR+). In order to examine the women with the breasts freely pendant, a special extension for the patient table made of carbon layer composite was designed. After data acquisition in the 3D modus, emission data were sorted into 2D sinograms using the Fourier rebinning algorithm and reconstructed by means of an ultra-fast iterative 2D algorithm (HOSP). The reconstructed emission scans were superimposed onto the corresponding transmission images. The protocol presented was evaluated in examinations on 6 women with breast lesions after the administration of 150-220 MBq F-18-FDG. From two adjacent bed positions, emission and transmission data were acquired over periods of 20 min and 10 min, respectively. For comparison, dynamic magnetic resonance (MR) image series were acquired with a whole-body MR system (MAGNETOM SP 4000) using a double-breast coil. RESULTS AND CONCLUSION: Using the designed extension of the patient table, it was possible to examine corpulent women despite the limited patient port of the PET system in the prone position with the breasts freely pendant. Alongside a reduction in motion artifacts, this positioning also offers the possibility of making a direct comparison between PET and MR images. Despite the fact that the amount of F-18-FDG applied to the patient was markedly reduced, the combination of 3D data acquisition and iterative image reconstruction resulted in excellent quality of the emission scans. By super-positioning of iteratively reconstructed emission and transmission scans, anatomical localization of breast lesions visualized on the emission scans could be improved. The postprocessing of the PET data described was completed in 60 min, this meaning that the presented concept can readily be employed in clinical practice.

Algorithms↗
PubMed1998

[Mucoepidermoid carcinoma of the submandibular gland after high-dose radioiodine therapy: case report and review of the literature].

Case report of a 42 year old female, who received 14th-20th year of life six radioiodine therapies with altogether 19.2 GBq131I because of a papillary thyroid carcinoma. 17 years after the last therapy, she developed a histologically proven chronic radiogenic sialadenitis of the left submandibular gland. Further four years later, the right submandibular gland has been extirpated because of a mucoepidermoid carcinoma with infiltration of a regionary lymphatic node. Review of the previous published secondary-malignancies of the salivary glands after high-dose radioiodine therapies.

Adult↗
PubMed1997

[99m-Tc-MIBI for recurrent and metastatic differentiated thyroid carcinoma].

AIM: The aim of the study has been the examination of the diagnostic value of 99mTc-MIBI scintigraphy for the detection of local tumor or metastases following total thyroidectomy and 131I ablation therapy in differentiated thyroid carcinoma. METHODS: MIBI-scintigraphy has been indicated in 85 patients because of ascending thyroglobulin values or suspected local recurrencies by ultrasonography. The results have been compared to cytology or histology or ultrasonography, computed tomography, X-ray and radioiodine scanning. RESULTS: MIBI scintigraphy was found positive in 32 of 40 metastases. Only 18 metastases have been seen by radioiodine. MIBI scintigraphy was most effective in detecting local tumor recurrencies and lymph node metastases (94%). The specificity of MIBI and radioiodine was similar (100%). In inflammatory enlarged lymph nodes no MIBI uptake was found, so it is possible to differentiate reactive lymph node enlargement from metastatic disease. CONCLUSION: In conclusion scintigraphy with 99mTc-MIBI is advisable in suspected local recurrencies and negative radioiodine scan. It is favourable that withdrawing TSH-suppressive hormone medication is not necessary.

Adult↗
PubMed1996

[Semiquantitative 99mTc-HMPAO SPECT in dementia of the Alzheimer type: influence of the selection of reconstruction filter and reference region].

AIM: The aim of the study was to clarify, whether the selection of the reference-region and/or the reconstruction-filter influences the result of the semiquantitative analysis of a 99mTc-HMPAO-SPECT that was conducted to diagnose the dementia of the Alzheimer type (DAT). METHODS: A group of 19 DAT-patients according to the criteria of NINCDS-ADRDA and DSM-III-R was examined together with a comparison group (n = 14) with normal cerebral perfusion. Three reference-regions (cerebellum, whole slice, occipital cortex) and four reconstruction-filters (Hanning fc = 0.7 and 1.0 Nyquist; Butterworth (n = 8); fc = 0.5 and 0.9 Nyquist) were applied to twelve standardized regions of interest (per patient) respectively. The data was evaluated through a ROC-analysis. RESULTS: It has been showed, that the bilateral parieto-temporal perfusion reduction as a characteristic of DAT depends on the filters and reference-regions used. The most secure separation of both groups of patients was obtained through a Butterworth-filter (n = 8; fc = 0.5) in combination with the cerebellum as reference-region. CONCLUSION: The selection of the reference-region and the reconstruction-filter has an important influence on the results of a semiquantitative analysis. Therefore standardisation in dependency on the actual questioning is necessary.

Aged↗
PubMed1992

Cyclin-B homologs in Saccharomyces cerevisiae function in S phase and in G2.

We have cloned four cyclin-B homologs from Saccharomyces cerevisiae, CLB1-CLB4, using the polymerase chain reaction and low stringency hybridization approaches. These genes form two classes based on sequence relatedness: CLB1 and CLB2 show highest homology to the Schizosaccharomyces pombe cyclin-B homolog cdc13 involved in the initiation of mitosis, whereas CLB3 and CLB4 are more highly related to the S. pombe cyclin-B homolog cig1, which appears to play a role in G1 or S phase. CLB1 and CLB2 mRNA levels peak late in the cell cycle, whereas CLB3 and CLB4 are expressed earlier in the cell cycle but peak later than the G1-specific cyclin, CLN1. Analysis of null mutations suggested that the CLB genes exhibit some degree of redundancy, but clb1,2 and clb2,3 cells were inviable. Using clb1,2,3,4 cells rescued by conditional overproduction of CLB1, we showed that the CLB genes perform an essential role at the G2/M-phase transition, and also a role in S phase. CLB genes also appear to share a role in the assembly and maintenance of the mitotic spindle. Taken together, these analyses suggest that CLB1 and CLB2 are crucial for mitotic induction, whereas CLB3 and CLB4 might participate additionally in DNA replication and spindle assembly.

Amino Acid Sequence↗
PubMed1991

A cyclin B homolog in S. cerevisiae: chronic activation of the Cdc28 protein kinase by cyclin prevents exit from mitosis.

A cyclin B homolog was identified in Saccharomyces cerevisiae using degenerate oligonucleotides and the polymerase chain reaction. The protein, designated Scb1, has a high degree of similarity with B-type cyclins from organisms ranging from fission yeast to human. Levels of SCB1 mRNA and protein were found to be periodic through the cell cycle, with maximum accumulation late, most likely in the G2 interval. Deletion of the gene was found not to be lethal, and subsequently other B-type cyclins have been found in yeast functionally redundant with Scb1. A mutant allele of SCB1 that removes an amino-terminal fragment of the encoded protein thought to be required for efficient degradation during mitosis confers a mitotic arrest phenotype. This arrest can be reversed by inactivation of the Cdc28 protein kinase, suggesting that cyclin-mediated arrest results from persistent protein kinase activation.

Alleles↗
PubMed1991

G1 control in yeast and animal cells.

In yeast G1, cyclins control the Cdc28 protein kinase in order to regulate the primary cell cycle gating event known as START. Environmental and internal signals that control the cell cycle do so, apparently, by controlling the synthesis and/or stability of G1 cyclins, hence controlling the activity of the Cdc28 kinase. The substrates of the Cdc28 kinase that are critical for passage through START are not known. One simple hypothesis is that the G1 kinase phosphorylates and thus activates a transcription factor required for the initiation of S phase. The synthesis of an origin of replication-binding factor might be regulated in this fashion. Recent evidence suggests that Cdc28 protein kinase activity directly regulates the transcription of a family of genes whose products are required for DNA replication (N. Marini and S. Reed, in prep.). However, it is not yet known whether this transcriptional activation constitutes the execution of START. The situation in animal cells is more complex. A number of new cyclins and p34s have been identified. It is not clear yet which of these, if any, have functions in G1 and if they do, what functions these might be. If G1 cyclins and p34 kinases do have critical G1 roles, by analogy with yeast, they may couple signals mediated by both positive and negative growth factors to cell cycle progression. Candidates for the critical G1 substrates of these putative G1 protein kinases are the tumor suppressors such as the RB (retinoblastoma) gene product (p105RB).(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1988

Effect of pteridines on normal and neoplastic cell lines of Xiphophorus.

The effect of three pteridines namely biopterin, isoxanthopterin and xanthopterin on cell growth, viability and morphology of three embryo and one melanoma derived cell lines was studied. Pteridines were assayed in the range of 10(-6) M to 10(-4) M. Biopterin exerted no influence on all cell lines tested, whereas isoxanthopterin and xanthopterin caused a decrease in growth rate with increasing concentrations. The strongest decrease of cell growth was exerted by 10(-4) M xanthopterin. Furthermore at this concentration xanthopterin reduced the viability of normal cells and influenced the morphology of both normal and neoplastic cells. In general, normal cells were more sensitive to pteridines than neoplastic cells.

Animals↗